Many therapeutically important natural products and pharmaceutical agents can be prepared from functionalized cyclopentane and dioxolane derivatives. The continued development of methodology for the efficient and stereoselective synthesis of these ring systems is proposed. This methodology is based on the free radical mediated addition of functionalized olefins or related species across the carbon-carbon bond of suitably activated vinylcyclopropanes to afford directly the cyclopentane units. Emphasis is placed on enhancing current levels of dia- stereoselectivity and enantioselectivity upon bond formation. Further, the development of novel free radical-based annelation/isomerization reactions for the construction of highly functionalized cyclopentanol species is planned. Finally, diastereoselective remote (Gamma) functionalization of secondary alcohols will be explored. Syntheses of the antitumor antibiotic brefeldin A and The antileukemic agent rocaglamide, which each utilize intramolecular variants of the cyclo- pentannelation process, will be investigated. Successful completion of these syntheses will afford the targets (or analogs) in the most efficient manner to date.